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vannic (Mechanical) (OP)
20 Feb 07 21:55
I'm an HVAC guy here.  Ran into one of my pumps that had its bearing fried.  Took a closer look and it's a 10hp motor with 6 leads.  My service guys typically deal with 9 lead motors.  There are 3 diagrams on the motor itself, a "Starting", one named "Delta running".  The leads were wired according to the "starting" diagram.  I purchased (I thought I purchased) a DOL motor but it sounds like I got a Wye-Delta motor.  Did the wiring cause the bearing failure? Also, is 6 leads for a 208-230/460V motor unusual?  Thanks
dbaird (Electrical)
21 Feb 07 6:04
Check:
http://www.joliet-equipment.com/terminal_markings_and_connections-3ph_motors-single_speed.htm

David Baird

Sr Controls Designer
EET degree.
Journeyman Electrician.

powerjunx (Electrical)
21 Feb 07 7:37
vannic,
 "Did the wiring cause the bearing failure? Also, is 6 leads for a 208-230/460V motor unusual?" dbaird had given you a great link, from EASA hanbook.
 Well,  i dont think wrong or faulty wiring is the root cause of such bearing failure its far beyond usual experience. Faulty wiring or wrong connection will trigger motor protection to trip.
 Usual bearing failure for general purpose motors are more on grease related application problem, misalignment, worn out bearing and loosen bearing housing. Thus, mechanical side is more subject for such failure.
 
petronila (Electrical)
21 Feb 07 8:15
Hello vannic,

Motor connection  don´t cause a Bearing failure.

If one motor is wrong connected you will notice about it by  Too High Current with protection devices trip,or  Too low Current and the motor can´t start due to poor torque or if the motor starts will burn shortly.The other chance is the motor don´t start an produce noise.

For a 6 Leads Motors you have the chance to connect for DOL in Wye or DOL in  Delta , Star Delta or Part Winding.But is necesary investigate in name plate or perform some test prior to starting in order to find the proper conection for the rated voltage.

Normally for Star Delta the leads are marked 1,2,3,4,5,and 6. For a  part Winding check if the leads are numbering 1,2,3,7,8 and 9.

If your motor was  running  well before the bearing damage then it was wired proper.

Regards

Petronila
resqcapt19 (Electrical)
21 Feb 07 16:10

Quote:

Also, is 6 leads for a 208-230/460V motor unusual?
How do you get that dual voltage rating with a 6 lead three phase motor?  If you have a 6 lead motor, the only two ways to connect it are wye or delta.  If that is the case the high and low voltages have to differ by a factor of 1.73.
Don
vannic (Mechanical) (OP)
21 Feb 07 16:42

Quote:



How do you get that dual voltage rating with a 6 lead three phase motor?  If you have a 6 lead motor, the only two ways to connect it are wye or delta.  If that is the case the high and low voltages have to differ by a factor of 1.73.
Don


That is exactly what I am worried about.  My tech says the label only says "start" and "run" which is indicative of a wye-delta motor.  Usually we see "low voltage" or "high voltage" for multi-voltage motors.  The motor was specified to be 208-230 or 460 volts.  The range between high and low is greater than 1.73.  I'm suspecting I got the wrong motor, it's been running on 460 and I thought that that had something to do with it's failure.  The company that made this motor is from Canada.  Everything that I've seen on 575 volt motors is a 6 lead motor.  Thanks.
petronila (Electrical)
22 Feb 07 8:09
Hello vannic,

For a Squirrel cage motors: 10 HP at 460 Volts Full -Load Current is 14. 10 HP at 575 Volts Full-Load Current is 11.

What amperage was drainning your motor at 460 V??

For NEMA motors normally the 6 leads windings design is unusual to operate  a 208-230/460V , for it you need 9 leads for DOL and 12 lead  for Star-Delta in each Voltage, for this last starting method the rated connection will be Delta for 460 and Two Deltas for 230 V.

In IEC Motors is very Usual a Dual Voltage Motor with 6 Leads, The Low Voltage Connection is Delta and the motor can start in Star-Delta.The High Voltage Connection is Star, in this case you will find the Voltage Ratio is 1.73. like a 220/380 Volts Motor.    

Taking account you sayd in last posts:

"Everything that I've seen on 575 volt motors is a 6 lead motor"

"it's been running on 460"

If the motor came from Canada in this countrie 575  is a standard Voltage, one way to find if your motor is 575 or 460 V is performing a no load test at 460 V if the current is less than 1.5 Amps the motor is for 575 V.For 460 volts we will wait  2.8 or 3.8 Amps.

The other chance is you received a remanufactured motor and the winding was redesigned for 460 but the shop did not install a new name plate.

I hope this could help you  

Regards

Petronila

    
resqcapt19 (Electrical)
22 Feb 07 11:30
Petronila,

Quote:

For NEMA motors normally the 6 leads windings design is unusual to operate  a 208-230/460V
How does that work?  The only way that I know of to operate at a different voltage with a six lead motor is to make the low voltage a delta connection and the high voltage a wye connection at the motor.  If the coils are rated for 230 volts and you connect them in a wye and provide a 480 volt supply, the coils will see 277 volts, well over the 230 volt design.  Do they just over build the coils for this purpose?
Don
petronila (Electrical)
22 Feb 07 12:37
Hello resqcap19,

Let me clear,   6 leads low voltage  NEMA motors are not capable to operate at both 208-230 /460 Volts.This 6 Leads Motors will work fine at only one of this Voltages, normally the 6 LEADS are  intended to start the motor in star-delta Starting.

For this Dual low voltage  Motors  Due to 460 V is twice 230 V,the NEMA winding design is made  with 9 or 12 leads. To operate at 230 Volts you made external conection called double connections  and to operate at 460 V you connect in single connections, the wye or Delta Connections depends of winding design but the 9 leads Motors can´t start in star delta starting. For dual Voltage 230/460 V, This start is possible only  with 12 Leads.  

NOTE: Made double connections for Low Voltages and Single Connections for High Voltages. The 230 Volts current is the twice of 460 V so you need double connection to support the twice of current.

For  IEC 6 leads  Motors or for Standard  Medium Voltage NEMA motors  you can perform a Delta CONNECTION for Low Voltage or Wye CONECTION for High Voltage . in this case you have the 1.73 Voltage Ratio.

Note: The Standards medium Voltage in USA are 2400 and 4160 Volts.In this case you have the 1.73 Voltage Ratio.(4160/2400).

Please take a look of the address recomended by dbair.

Regards

Petronila

resqcapt19 (Electrical)
22 Feb 07 13:05
Petronila,

Quote:

Let me clear,   6 leads low voltage  NEMA motors are not capable to operate at both 208-230 /460 Volts.This 6 Leads Motors will work fine at only one of this Voltages, normally the 6 LEADS are  intended to start the motor in star-delta Starting.
Thanks, I wasn't clear on what you were saying in the earlier post.  
Don
dV8r (Electrical)
22 Feb 07 14:31
If the motor, being run with the start windings only caused it to overheat, it would also cause premature bearing failure.
waross (Electrical)
22 Feb 07 22:28
I have seen a few 575 volt motors in Canada, but they were all three lead. I've never seen a six lead 575 volt motor.
This could be a part winding start motor.
it could also be a mistake at the winding shop.
respectfully
vannic (Mechanical) (OP)
23 Feb 07 11:18
I'd like to thank everyone for their inputs.  One thing is for sure, the motor we have is definitely not the one that we were supposed to have purchased.  The motor manufacturer's website has an online selection tool and it has the motor that was specified should be a 9-lead motor.  We're working with the pump people now to change the motors.  Thanks again.

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